The present invention relates to an equipment for producing industrial-use tapering poles for lighting and similar applications.
It is known that industrial-use poles and in particular poles designed to support telephone cables and cables for electric energy transport can be made of different types of materials.
Poles made of wood, reinforced concrete or steel are the most traditional ones.
Poles made of wood are economical, mechanically strong and resilient, above all if impregnated with appropriate resins. However they do not have a long lifetime and are not satisfactory from an ecological point of view both because they give rise to deforestation and because they emit toxic fumes resulting from the impregnating substances, when they are destroyed by combustion at the end of their life.
Reinforced concrete poles have some qualities as well, such as structural strength, reasonable costs and acceptable surface appearance, but they have a serious drawback in that their iron part can be chemically attacked through surface cracks and splits formed therein in time, and therefore they can undergo deterioration in a rather short period of time. In addition, it is clear that their destruction is difficult and troublesome.
Iron poles have excellent strength features and reasonable costs, but, on the other hand, they need frequent servicing works tending to avoid rust formation and to enable them to resist chemical attacks above all in sea salt-rich media.
Other types of materials based on the use of "rovings" of artificial fibers such as glass fibers, impregnated with synthetic resins, polyesters for example, are known too.
These materials have many advantages. In fact they are not attacked by weather agents, not even sea salts, practically have an unlimited lifetime, do not need to be painted and do not change colour by effect of UV rays.
Several different technologies for manufacturing poles are known, in particular for manufacturing internally-hollow tapering poles, which are generally preferred because they enable both weight and cost to be reduced.
In one of these known technologies a roving previously impregnated with synthetic resins is wound on a rotating mandrel by means of appropriate delivery carriages movable along the mandrel axis. The mandrel covered with the desired amount of the above fibers is transferred to an oven for hardening of the material. Subsequently it is removed from the oven and the separation between the mandrel and the now hardened cover constituting the pole is carried out by means of presses. Not only the above described production process has big problems during the step of extracting the mandrel from the pole, but it also gives rise to poles having rough surfaces.
In a second known technology for manufacturing poles of fiber materials, a roving impregnated with resins or a non-impregnated fiber fabric is wound as in the previous case around a mandrel. Subsequently the thus coated mandrel is introduced into a heated mould the sizes of which correspond to those of the mandrel itself. If non-impregnated fabrics are used, the intended resin is then injected into said mould. In this second case as well, the pole surface is not particularly smooth and irregularities can occur in the distribution of the fibers and, as a result, the mechanical strength is reduced.
In a third type of production process provision is made for the use of a rotating heated die the shape of which matches the shape of the outer surface of the pole to be produced. When the die is stationary, a mandrel is introduced thereinto, on which mandrel layers of fabric have been previously wound so as to make the desired variations in the pole diameter. When the die is set in rotation the fabric will tend to adhere to the die itself by centrifugal force, and simultaneously resin for impregnating the different fabric layers will be admitted thereinto.
Although poles obtained by adopting the last mentioned production technology have an excellent surface appearance and good mechanical strength, they however involve the use of equipments having inelasticity in operation (if it is considered that each machine can make poles of three or four lengths which however have one taper only). In addition the use of particular fabrics or composite materials manufactured by specialized firms, makes prices rise.